A need exists for frequent adjustment of brakes in motor vehicles, particularly trucks. Efforts have been made to effect automatic adjustment whenever a brake is applied. A lever is operated whenever a brake is applied, and means must be provided so that the lever effects tightening adjustment when moved in one direction, and holds parts in place without movement upon return of the lever to its normal or rest position.
The drive or force transmission from the lever to the tightening mechanism must be positive in the desired tightening direction and capable of transmitting substantial force. Similar requirements pertain for other devices, such as ratchet wrenches.